1. Field of the Invention
The present invention relates to an image processing device having an image data generator generating image data which consists of a plurality of color data and is an image information for each pixel, an image data output unit outputting the image data to the outside of the device, and an image display unit displaying an image using the image data consisting of a plurality of color data, and in particular to an image processing device performing image processing on the image data, in accordance with the color reproduction characteristics of the image display unit provided in a notebook-type personal computer or the like.
2. Conventional Art
FIG. 19 is a block diagram showing an example of configuration of a conventional image processing device. In the drawing, reference numeral 1 denotes an image data generator, 2 denotes an image display unit, and 3 denotes an image data output unit. The image data generator 1 generates and outputs first color data R1, G1, B1 constituting first image data. R1, G1, B1 respectively denote color data representing red, green and blue, respectively. The first color data R1, G1, B1 are input to the image display unit 2 and the image data output unit 3. The image display unit 2 is formed for example of a liquid crystal panel, and generates an image which can be visually perceived by a human being based on the first color data R1, G1, B1, and displays the generated image. The image data output unit 3 outputs the first color data R1, G1, B1 to the outside. For instance, a notebook-type personal computer has a configuration as shown in FIG. 19.
FIG. 20 is a block diagram showing an example of the image data generator 1. As illustrated, it comprises an image data 4, an image data reader 5, and a frame buffer 6. The image data storage 4 stores a plurality of image data in advance. The image data reader 5 reads out appropriate image data R10, G10, B10 from among a plurality of image data stored in the image data storage 4, and writes the image data in the frame buffer 6, at a writing rate. The image data is read out of the frame buffer 6 at a reading rate in conformity with the image display rate, and output as the first image data.
Each image display unit 2 has a unique color reproduction characteristics. FIG. 21 is an xy chromaticity diagram illustrating the color reproduction characteristics of liquid crystal panels used in notebook-type personal computers. Each of the three triangles depicted by the solid line represents the color gamut of each of three types of liquid crystal panels. The vertexes of each triangle represents the color reproduction (or rendition) of red, green and blue. The triangle depicted by the broken lines represents the color gamut of the standard color space sRGB stipulated by IEC61966-2-1. The difference in the color gamut leads to difference in the color reproduction characteristics if no image processing such as color conversion is applied.
It is observed from FIG. 21 that the color reproduction characteristics of each liquid crystal panel is different from the color reproduction characteristics according to the sRGB which is a standard color space. Moreover, different types of liquid crystal panels have different color reproduction characteristics. Display units other than liquid crystal panels have yet different color reproduction characteristics. Accordingly, the color reproduction of the image displayed on the image display unit 2 in the conventional image processing device differs substantially depending on the color reproduction characteristics of the image display unit, and it was not possible to realize an “exact color reproduction” which is a color reproduction as intended by the image creator. Moreover, it was not possible to realize a “preferred color reproduction” which is a color reproduction as preferred by the user.
It can be conceived to solve this problem by reflecting the color reproduction characteristics of the image display unit 2, when generating the first color data at the image data generator 1. FIG. 22 shows another example of configuration of the image data generator 1. Members 4, 5 and 6 are identical to those in FIG. 20. The image data generator 1 of the illustrated example further includes a color converter 7, which converts the image data R10, G10, B10, into the first color data R1, G1, B1 constituting the first image data. The conversion from the image data R10, G10, B10 to the first color data R1, G1, B1 can be achieved by the following equation (1).
                              [                                                                      R                  ⁢                                                                          ⁢                  1                                                                                                      G                  ⁢                                                                          ⁢                  1                                                                                                      B                  ⁢                                                                          ⁢                  1                                                              ]                =                              (                          A              ⁢                                                          ⁢              i              ⁢                                                          ⁢              j                        )                    ⁡                      [                                                                                R                    ⁢                                                                                  ⁢                    10                                                                                                                    G                    ⁢                                                                                  ⁢                    10                                                                                                                    B                    ⁢                                                                                  ⁢                    10                                                                        ]                                              (        1        )            
In the equation (1), i=1 to 3, j=1 to 3.
The matrix coefficients Aij in the equation (1) are determined based on the color reproduction characteristics of the image display unit 2. For instance, the coefficients are so determined that the relationship between the image data R10, G10, B10 and the chromaticity of the colors displayed on the image display unit 2 is closest to the relationship stipulated by the standard color space sRGB.
When this condition is met, the first color data R1, G1, B1 are data reflecting the color reproduction characteristics of the image display unit 2. The first color data R1, G1, B1 are also output via the image data output unit 3 to the outside. The image data output to the outside may be supplied to various image processing devices, or image display devices, so that it is preferred that they do not reflect the characteristics of a specific device, but have a standard characteristics. For instance, if the color reproduction characteristics of the image display unit 2 is such that red is displayed as magentish red (red tinged with magenta), the color converter 7 shown in FIG. 22 performs such processing that red is converted to and hence displayed as yellowish red, for the correction of the magentish red, in producing the first color data. The first color data is output through the image data output unit 3 to the outside. If the first color data is supplied to an image display device having such a characteristics that red is displayed as yellowish red, the yellowishness is emphasized.
Also, it is becoming a standard practice in color management to exchange, between devices, data according the standard color space such as sRGB, and the correction of the color reproduction characteristics of individual devices is effected in respective devices. This is another reason why the image data output to the outside should not reflect the color reproduction characteristics of the image display unit.
As has been described, in a conventional image processing device, the color reproduction of the image displayed by the image display unit differs very much depending on the color reproduction characteristics of the particular image display unit, and it is often impossible to achieve an “exact color reproduction.” Moreover, it is often impossible to achieve a “preferred color reproduction” which is a color reproduction preferred by the user. Moreover, if the image data is generated to be suitable for the color reproduction characteristics of the image display unit, the image data output to the outside becomes one which reflects the color reproduction characteristics of the image data display unit, and, in the image processing device or an image display device that is externally connected to receive the output image data, it is not possible to realize an “exact color reproduction,” or “preferred color reproduction.” In a worst combination of the characteristics of the image processing device and the characteristics of the externally connected image display device, the image displayed by the image display device connected outside may collapse.